Container-based language runtime loading an isolated method

ABSTRACT

Embodiments include a code loader method for loading attributes corresponding to an isolated method by a container-based language runtime. The attributes are received by the container-based language runtime without any specified container for storage of the isolated method attributes. The attributes received as parameters of code loader method and include instructions, live objects, and parameter types corresponding to the isolated method. The container-based language runtime selects a first-order container for storing the attributes of the isolated method.

INCORPORATION BY REFERENCE; DISCLAIMER

Each of the following applications are hereby incorporated by reference:application Ser. No. 16/241,503 filed on Jan. 7, 2019; application Ser.No. 15/664,994 filed on Jul. 31, 2017; application No. 62/369,190 filedon Jul. 31, 2016. The Applicant hereby rescinds any disclaimer of claimscope in the parent application(s) or the prosecution history thereofand advises the USPTO that the claims in this application may be broaderthan any claim in the parent application(s).

TECHNICAL FIELD

The present disclosure relates to the use of isolated methods. Inparticular, the present disclosure relates to a container-based languageruntime selecting a container for maintaining an isolated method in acontainer-based language framework.

BACKGROUND

A class-based programming model is a style of object-orientedprogramming. In this model, classes define blueprints or templates.Classes are instantiated to generate objects in accordance with theblueprints or templates defined by the class.

A class is compiled to generate a class file (expressed as bytecode)which may include, but is not limited to fields, methods, name of sourcefile that includes the class, interfaces, name of the class, super classof the class, access flags (abstract, static, etc.), pool of constantsfor the class, and a version number of the class file. Accordingly, eachclass file serves a “container” of a multitude of components includingmethods. Similarly, different programming languages/models make use ofcontainers which may include methods.

Bytecode processed by a container-based programming language runtimetypically adheres to a particular container format expected by thecontainer-based programming language runtime. Methods, to be executed bythe container-based programming language runtime, are included withincontainers that adhere to the particular container format.

The approaches described in this section are approaches that could bepursued, but not necessarily approaches that have been previouslyconceived or pursued. Therefore, unless otherwise indicated, it shouldnot be assumed that any of the approaches described in this sectionqualify as prior art merely by virtue of their inclusion in thissection.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments are illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings. It should benoted that references to “an” or “one” embodiment in this disclosure arenot necessarily to the same embodiment, and they mean at least one. Inthe drawings:

FIG. 1 illustrates an example container-based language architecture inaccordance with one or more embodiments;

FIG. 2A illustrates an example structure of a construct-based containerthat is generated by compiling a construct in a container-based languageframework in accordance with one or more embodiments;

FIG. 2B illustrates an example components of an Isolated Method (IM)container in accordance with one or more embodiments;

FIG. 3 illustrates an example virtual machine memory layout 300 in blockdiagram form in accordance with one or more embodiments;

FIG. 4 illustrates an example frame 400 in block diagram in accordancewith one or more embodiments;

FIG. 5 illustrates an example set of operations for loading an isolatedmethod by a container-based language runtime in accordance with one ormore embodiments;

FIG. 6 illustrates a garbage collection process for reclaiming portionsof memory allocated to an IM container in accordance with one or moreembodiments;

FIG. 7 illustrates a system in accordance with one or more embodiments.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding. One or more embodiments may be practiced without thesespecific details. Features described in one embodiment may be combinedwith features described in a different embodiment. In some examples,well-known structures and devices are described with reference to ablock diagram form in order to avoid unnecessarily obscuring the presentinvention.

-   -   1. GENERAL OVERVIEW    -   2. ARCHITECTURAL OVERVIEW        -   2.1 EXAMPLE CLASS FILE STRUCTURE        -   2.2 EXAMPLE STRUCTURE OF AN ISOLATED METHOD CONTAINER        -   2.3 EXAMPLE VIRTUAL MACHINE ARCHITECTURE        -   2.4 LOADING, LINKING, AND INITIALIZING CLASSES    -   3. LOADING AN ISOLATED METHOD    -   4. GARBAGE COLLECTION OF CONTAINER COMPONENTS    -   5. MISCELLANEOUS; EXTENSIONS    -   6. HARDWARE OVERVIEW        1. General Overview

One or more embodiments relate to a container-based language runtimethat imposes a container-based object orientation for the organizationof code. The container-based language runtime processes componentsorganized within containers that adhere to a container format. Thecontainer format is recognized and traversable by the correspondingcontainer-based language runtime. A Java class file is an example of acontainer that adheres to a container format. Components organizedwithin a container may include, but are not limited to fields, methods,flags, metadata, identification of related containers, version numbers,constants, etc. Containers, referred to herein, include “first-order”containers which are containers of a highest level (or largest size) ina hierarchical system of containers. First-order containers arecontainers that may be processed or maintained by a container-basedlanguage runtime.

The Java runtime environment is an example of a container-based languageruntime environment that imposes a container-based object orientationfor the organization of code. The “containers” processed by the Javaruntime environment correspond to class files which contain fields,methods, flags, metadata, identification of related containers, versionnumbers, constants, etc. Containers that are submitted to the Javaruntime environment as input may be referred to herein as “first-order”or “first-level” containers, which may themselves includesub-containers. Data is organized in relation to “first-order”containers by the Java runtime environment.

As an example, a user may specify a method as a component of aparticular class (“construct”) which is compiled to generate acorresponding class file (“construct-based container”). The class file,to be processed by the Java runtime environment, includes the attributesof the method. The attributes may include, but are not limited to amethod type (including parameter types and return value), method name,method instructions, and constants referenced by the methodinstructions.

A container, submitted to a container-based language runtimeenvironment, may be generated by compilation of a construct. Examples ofconstructs include, but are not limited to, a class defined by aprogrammer, a class defined in a programming language API, and/or aclass generated by a runtime environment (e.g., during the processing ofan annotation). A container, that is generated by compilation of aconstruct, (a) represents that construct and (b) is referred to hereinas a “construct-based container.” A method may be defined as a componentof a construct which is compiled to generate the construct-basedcontainer. Method attributes of such a method are stored by the runtimeenvironment as a component of the construct-based container.

In an embodiment, the container-based language runtime receives methodattributes, defining a method, without any construct-based container inrelation to which the method attributes are to be stored. For example, acode loader method (e.g., “loadcode” method referred to herein) isspecified as a component of a particular construct-based container. Theattributes of another method (referred to herein as an “isolatedmethod”) are received as parameters of the code loader method, withoutidentification of a specific container to which the isolated methodbelongs. Any such method, received by the container-based languageruntime without a corresponding construct-based container of the method,is referred to herein as an “isolated method.”

In an embodiment, a container-based language runtime includesfunctionality to generate a container without receiving anidentification of any corresponding construct, or compilation of theconstruct. The container-based language runtime generates a container,without any compilation of a construct, for storing the attributes of anisolated method. The container generated by the container-based languageruntime for storing the attributes of the Isolated Method (IM) may bereferred to herein as an “Isolated Method (IM) container.”

An IM container may include a different organizational structure than aconstruct-based container. For example, an IM container may include asimpler organizational structure than a construct-based container. An IMcontainer may simply correspond to metadata identifying where theattributes of the isolated method are stored and/or how the isolatedmethod may be invoked. An IM container may be defined using (a) asmaller set of metadata than a construct-based container and/or (b) havea fewer set of component types than a construct-based container. As aresult, a container-based language runtime may traverse an IM containerto access respective method attributes in less time than aconstruct-based container. Accordingly, an IM container may have asmaller “footprint” than a construct-based container. The IM containerand the construct-based containers may both be recognizable andtraversable by an associated container-based language runtime.

In an embodiment, the IM attributes received by the container-basedlanguage runtime include a Constants array. The Constants array includesconstants referenced by the IM instructions. Any type of object may beincluded in the Constants array. The Constants array may provide ahigher level of abstraction than a traditional Constant pool referencedby methods of construct-based containers.

One or more embodiments described in this Specification and/or recitedin the claims may not be included in this General Overview section.

2. Architectural Overview

FIG. 1 illustrates an example container-based language architecture(“computing architecture 100) in which techniques described herein maybe practiced. Software and/or hardware components described withrelation to the example architecture may be omitted or associated with adifferent set of functionality than described herein. Software and/orhardware components, not described herein, may be used within anenvironment in accordance with one or more embodiments. Accordingly, theexample environment should not be constructed as limiting the scope ofany of the claims.

Embodiments relate to the generation and processing of “containers” by acontainer-based language framework as described in detail below. A“class file” is an example of a container. Embodiments and examplesreferencing a “class file” may be equally applicable to other kinds ofcontainers in any container-based language framework.

FIG. 1 includes a computing architecture 100 used for processing sourcecode files 101. Generally, source code files 101 are compiled by acompiler 102 into class files 103 representing the program to beexecuted. Components of the class files 103 are loaded and executed byan execution platform 112 which includes a runtime environment 113, anoperating system 111, and one or more application programming interfaces(APIs) 110. APIs 110 enable communication between the runtimeenvironment 113 and the operating system 111. The runtime environment113 includes a virtual machine 104 comprising various components, suchas a memory manager 105 (which may include a garbage collector), a classfile verifier 106 to check the validity of class files 103, a classloader 107 to locate and build in-memory representations of classes, aninterpreter 108 for executing the virtual machine 104 code, and ajust-in-time (JIT) compiler 109 for producing optimized machine-levelcode.

In an embodiment, the computing architecture 100 includes source codefiles 101 that contain code that has been written in a particularprogramming language, such as Java, C, C++, C#, Ruby, Perl, and soforth. Thus, the source code files 101 adhere to a particular set ofsyntactic and/or semantic rules for the associated language. Forexample, code written in Java adheres to the Java LanguageSpecification. However, since specifications are updated and revisedover time, the source code files 101 may be associated with a versionnumber indicating the revision of the specification to which the sourcecode files 101 adhere. The exact programming language used to write thesource code files 101 is generally not critical.

In order to provide clear examples, the source code files 101 have beenillustrated as the “top level” representation of the program to beexecuted by the execution platform 111. Although the computingarchitecture 100 depicts the source code files 101 as a “top level”program representation, in other embodiments the source code files 101may be an intermediate representation received via a “higher level”compiler that processed code files in a different language into thelanguage of the source code files 101. Some examples in the followingdisclosure assume that the source code files 101 adhere to a class-basedobject-oriented programming language. However, this is not a requirementto utilizing the features described herein.

In various embodiments, the compiler 102 compiles the source code, whichis written according to a specification directed to the convenience ofthe programmer, to either machine or object code, which is executabledirectly by the particular machine environment, or an intermediaterepresentation (“virtual machine code/instructions”), such as bytecode,which is executable by a virtual machine 104 that is capable of runningon top of a variety of particular machine environments. The virtualmachine instructions are executable by the virtual machine 104 in a moredirect and efficient manner than the source code. Compiling source codeto generate virtual machine instructions includes mapping source codefunctionality from the language to virtual machine functionality thatutilizes underlying resources, such as data structures. Often,functionality that is presented in simple terms via source code by theprogrammer is converted into more complex steps that map more directlyto the instruction set supported by the underlying hardware on which thevirtual machine 104 resides.

In general, programs are executed either as a compiled or an interpretedprogram. When a program is compiled, the code is transformed globallyfrom a first language to a second language before execution. Since thework of transforming the code is performed ahead of time; compiled codetends to have excellent run-time performance. In addition, since thetransformation occurs globally before execution, the code can beanalyzed and optimized using techniques such as constant folding, deadcode elimination, inlining, and so forth. However, depending on theprogram being executed, the startup time can be significant. Inaddition, inserting new code would require the program to be takenoffline, re-compiled, and re-executed. For many dynamic languages (suchas Java) which are designed to allow code to be inserted during theprogram's execution, a purely compiled approach may be inappropriate.When a program is interpreted, the code of the program is readline-by-line and converted to machine-level instructions while theprogram is executing. As a result, the program has a short startup time(can begin executing almost immediately), but the run-time performanceis diminished by performing the transformation on the fly. Furthermore,since each instruction is analyzed individually, many optimizations thatrely on a more global analysis of the program cannot be performed.

In some embodiments, the virtual machine 104 includes an interpreter 108and a JIT compiler 109 (or a component implementing aspects of both),and executes programs using a combination of interpreted and compiledtechniques. For example, the virtual machine 104 may initially begin byinterpreting the virtual machine instructions representing the programvia the interpreter 108 while tracking statistics related to programbehavior, such as how often different sections or blocks of code areexecuted by the virtual machine 104. Once a block of code surpasses athreshold (is “hot”), the virtual machine 104 invokes the JIT compiler109 to perform an analysis of the block and generate optimizedmachine-level instructions which replaces the “hot” block of code forfuture executions. Since programs tend to spend most time executing asmall portion of overall code, compiling just the “hot” portions of theprogram can provide similar performance to fully compiled code, butwithout the start-up penalty. Furthermore, although the optimizationanalysis is constrained to the “hot” block being replaced, there stillexists far greater optimization potential than converting eachinstruction individually. There are a number of variations on the abovedescribed example, such as tiered compiling.

Referring back to the compiler 102, the compiler 102 compiles the sourcecode files 101 to generate class files 103 that are in a format expectedby the virtual machine 104. For example, in the context of the JVM, theJava Virtual Machine Specification defines a particular class fileformat to which the class files 103 are expected to adhere. In someembodiments, the class files 103 contain the virtual machineinstructions that have been converted from the source code files 101.Class files 103 may contain other structures as well, such as tablesidentifying constant values and/or metadata related to variousstructures (classes, fields, methods, and so forth).

In some embodiments, the class files 103 are divided into one or more“libraries” or “packages”, each of which includes a collection ofclasses that provide related functionality. For example, a library maycontain one or more class files that implement input/output (I/O)operations, mathematics tools, cryptographic techniques, graphicsutilities, and so forth. Further, some classes (or fields/methods withinthose classes) may include access restrictions that limit their use towithin a particular class/library/package or to classes with appropriatepermissions.

A “first-order” or “first-level” container, submitted to acontainer-based language runtime environment, is a container that may begenerated by compilation of a construct. Examples of constructs include,but are not limited to, a class defined by a programmer, a class definedin a programming language API, and/or a class generated by a runtimeenvironment (e.g., during the processing of an annotation). A containergenerated by compilation of a construct represents that construct, andis referred to herein as a “construct-based container.” As an example,as class files 103 are construct-based containers that representcorresponding constructs, i.e., classes defined in source code files 101or classes dynamically generated by the compiler 102/ virtual machine104.

In contrast to “construct-based containers” described above, one or moreembodiments include containers that do not directly correspond to acompiled version of a corresponding construct, and therefore do notnecessarily represent any construct. These containers, which do notdirectly correspond to a compiled version of a corresponding construct,are containers generated by a container-based runtime environment.

In an embodiment, a container-based language runtime generates acontainer, without any compilation of a construct, for storing theattributes of an isolated method. The container generated by thecontainer-based language runtime for storing the attributes of theIsolated Method (IM) may be referred to herein as an “Isolated Method(IM) container.”

An IM container may include a different organizational structure than aconstruct-based container. For example, an IM container may include asimpler organizational structure than a construct-based container. An IMcontainer may simply correspond to metadata identifying where theattributes of the isolated method are stored and/or how the isolatedmethod may be invoked. Since an IM container is not based on aconstruct, such as a class, the IM container does not capture the manycomponents of a typical construct in a programming language. An IMcontainer may be defined using (a) a smaller set of metadata than aconstruct-based container and/or (b) have a fewer set of component typesthan a construct-based container. As a result, a container-basedlanguage runtime may traverse an IM container to access respectivemethod attributes in less time than a construct-based container.Accordingly, an IM container may have a smaller “footprint” than aconstruct-based container. The IM container and the construct-basedcontainers may both be recognizable and traversable by an associatedcontainer-based language runtime.

Class file 120, illustrated in FIG. 1, is an example of an IM containergenerated by runtime environment 113. Differences betweenconstruct-based containers and IM containers are further explored below.

2.1 Example Structure of a Construct-Based Container

FIG. 2A illustrates class file 200 a, an example structure of aconstruct-based container that is generated by compiling a construct ina container-based language framework. Other construct-based containersmay have more, less, or different components than the illustratedconstruct-based container. The construct-based container refers to aspecific kind of construct-based container, a class file for purposes ofexplanation. In order to provide clear examples, the disclosure mayassume that class files 103 of the computing architecture 100 adhere tothe structure of the example class file 200 a described in this section.However, in a practical environment, the structure of the class file 200a will be dependent on the implementation of the virtual machine 104.Further, one or more features discussed herein may modify the structureof the class file 200 a to, for example, add additional structure types.Therefore, the exact structure of the class file 200 a is not criticalto the techniques described herein. For the purposes of Section 2.1,“the class” or “the present class” refers to the class represented bythe class file 200 a.

In FIG. 2A, the class file 200 a includes a constant table 201, fieldstructures 208, class metadata 207, and method structures 209. In anembodiment, the constant table 201 is a data structure which, amongother functions, acts as a symbol table for the class. For example, theconstant table 201 may store data related to the various identifiersused in the source code files 101 such as type, scope, contents, and/orlocation. The constant table 201 has entries for value structures 202(representing constant values of type int, long, double, float, byte,string, and so forth), class information structures 203, name and typeinformation structures 204, field reference structures 205, and methodreference structures 206 derived from the source code files 101 by thecompiler 102. In an embodiment, the constant table 201 is implemented asan array that maps an index i to structure j. However, the exactimplementation of the constant table 201 is not critical.

In some embodiments, the entries of the constant table 201 includestructures which index other constant table 201 entries. For example, anentry for one of the value structures 202 representing a string may holda tag identifying its “type” as string and an index to one or more othervalue structures 202 of the constant table 201 storing char, byte or intvalues representing the ASCII characters of the string.

In an embodiment, field reference structures 205 of the constant table201 hold an index into the constant table 201 to one of the classinformation structures 203 representing the class defining the field andan index into the constant table 201 to one of the name and typeinformation structures 204 that provides the name and descriptor of thefield. Method reference structures 206 of the constant table 201 hold anindex into the constant table 201 to one of the class informationstructures 203 representing the class defining the method and an indexinto the constant table 201 to one of the name and type informationstructures 204 that provides the name and descriptor for the method. Theclass information structures 203 hold an index into the constant table201 to one of the value structures 202 holding the name of theassociated class.

The name and type information structures 204 hold an index into theconstant table 201 to one of the value structures 202 storing the nameof the field/method and an index into the constant table 201 to one ofthe value structures 202 storing the descriptor.

In an embodiment, class metadata 207 includes metadata for the class,such as version number(s), number of entries in the constant pool,number of fields, number of methods, access flags (whether the class ispublic, private, final, abstract, etc.), an index to one of the classinformation structures 203 of the constant table 201 that identifies thepresent class, an index to one of the class information structures 203of the constant table 201 that identifies the superclass (if any), andso forth.

In an embodiment, the field structures 208 represent a set of structuresthat identifies the various fields of the class. The field structures208 store, for each field of the class, accessor flags for the field(whether the field is static, public, private, final, etc.), an indexinto the constant table 201 to one of the value structures 202 thatholds the name of the field, and an index into the constant table 201 toone of the value structures 202 that holds a descriptor of the field.

In an embodiment, the method structures 209 represent a set ofstructures that identifies the various methods of the class. The methodstructures 209 store, for each method of the class, accessor flags forthe method (e.g. whether the method is static, public, private,synchronized, etc.), an index into the constant table 201 to one of thevalue structures 202 that holds the name of the method, an index intothe constant table 201 to one of the value structures 202 that holds thedescriptor of the method, and the virtual machine instructions thatcorrespond to the body of the method as defined in the source code files101.

In an embodiment, a descriptor represents a type of a field or method.For example, the descriptor may be implemented as a string adhering to aparticular syntax. While the exact syntax is not critical, a fewexamples are described below.

In an example where the descriptor represents a type of the field, thedescriptor identifies the type of data held by the field. In anembodiment, a field can hold a basic type, an object, or an array. Whena field holds a basic type, the descriptor is a string that identifiesthe basic type (e.g., “B”=byte, “C”=char, “D”=double, “F”=float,“I”=int, “J”=long int, etc.). When a field holds an object, thedescriptor is a string that identifies the class name of the object(e.g. “L ClassName”). “L” in this case indicates a reference, thus “LClassName” represents a reference to an object of class ClassName. Whenthe field is an array, the descriptor identifies the type held by thearray. For example, “[B” indicates an array of bytes, with “[”indicating an array and “B” indicating that the array holds the basictype of byte. However, since arrays can be nested, the descriptor for anarray may also indicate the nesting. For example, “[[L ClassName”indicates an array where each index holds an array that holds objects ofclass ClassName. In some embodiments, the ClassName is fully qualifiedand includes the simple name of the class, as well as the pathname ofthe class. For example, the ClassName may indicate where the file isstored in the package, library, or file system hosting the class file200 a.

In the case of a method, the descriptor identifies the parameters of themethod and the return type of the method. For example, a methoddescriptor may follow the general form “({ParameterDescriptor})ReturnDescriptor”, where the {ParameterDescriptor} is a list of fielddescriptors representing the parameters and the ReturnDescriptor is afield descriptor identifying the return type. For instance, the string“V” may be used to represent the void return type. Thus, a methoddefined in the source code files 101 as “Object m(int I, double d,Thread t) {. . . }” matches the descriptor “(I D L Thread) L Object”.

In an embodiment, the virtual machine instructions held in the methodstructures 209 include operations which reference entries of theconstant table 201. Using Java as an example, consider the followingclass:

class A { int add12and13( ) { return B.addTwo(12, 13); } }

In the above example, the Java method add12and13 is defined in class A,takes no parameters, and returns an integer. The body of methodadd12and13 calls static method addTwo of class B which takes theconstant integer values 12 and 13 as parameters, and returns the result.Thus, in the constant table 201, the compiler 102 includes, among otherentries, a method reference structure that corresponds to the call tothe method B.addTwo. In Java, a call to a method compiles down to aninvoke command in the bytecode of the JVM (in this case invokestatic asaddTwo is a static method of class B). The invoke command is provided anindex into the constant table 201 corresponding to the method referencestructure that identifies the class defining addTwo “B”, the name ofaddTwo “addTwo”, and the descriptor of addTwo “(I I)I”. For example,assuming the aforementioned method reference is stored at index 4, thebytecode instruction may appear as “invokestatic #4”.

Since the constant table 201 refers to classes, methods, and fieldssymbolically with structures carrying identifying information, ratherthan direct references to a memory location, the entries of the constanttable 201 are referred to as “symbolic references”. One reason thatsymbolic references are utilized for the class files 103 is because, insome embodiments, the compiler 102 is unaware of how and where theclasses will be stored once loaded into the runtime environment 113. Aswill be described in Section 2.3, eventually the run-time representationof the symbolic references is resolved into actual memory addresses bythe virtual machine 104 after the referenced classes (and associatedstructures) have been loaded into the runtime environment and allocatedconcrete memory locations.

2.2 Example Structure of an Isolated Method Container

An Isolated Method (IM) container is a container generated by acontainer-based language runtime in accordance with one or moreembodiments. As noted above, in contrast to a construct-based container,the IM container does not directly represent a compiled version of aconstruct in a container-based language. An IM container is synthesizedas needed by the container-based language runtime.

Since an IM container is not a compiled version of a construct, an IMcontainer does not capture all the information of any construct that maytypically be captured in a construct-based container. While an IMcontainer may include any of components of a construct-based containerdescribed above, it is not necessary for an IM container to include allof the components of a construct-based container. Depending on theimplementation, an IM container does not necessarily adhere to the sameformat/structure of a construct-based container. An IM container mayinstead include only the components necessary for (a) referencing theattributes of an isolated method, and (b) processing by acontainer-based language runtime. Accordingly, an IM container mayinclude a much simpler organizational structure than a construct-basedcontainer. In an example, an IM container includes metadata that (a)adheres to a format recognizable/traversable by a container-basedlanguage runtime and (b) identifies the attributes of one or moreisolated methods. The container-based language runtime may be configuredto process at least two different kinds of containers with respectiveorganizational structures: the construct-based container and the IMcontainer.

In an embodiment, the IM container may be a “stretchable” and/or“shrinkable” container that includes the attributes of isolated methodsthat have “live” references. “Live” references correspond to currentlyreferenceable, instantiated objects (e.g.,java.lang.invoke.MethodHandles defined in the Java API) that may be usedto invoke an isolated method. As a number of isolated methods storedwithin an IM container increases, the IM container may increase in size.In some embodiments, there is no limit on the size of an IM container;the IM container may be referred to herein as a “gargantuan” IMcontainer. In other embodiments, a limited size or limited number ofisolated methods for an IM container may be enforced. Additional detailsregarding the process of creating, updating, or terminating the IMcontainer are described below.

An IM container may be defined per group of isolated methods, includingthe attributes of the corresponding group of isolated methods. In anexample, an IM container is created per module with at least oneisolated method. Isolated methods corresponding to a same module in amodule system may be grouped into a same IM container. An example of amodule system is described in U.S. Non-Provisional application Ser. No.14/808,689 filed on Jul. 24, 2015, titled “Bridging a Module System anda Non-Module System”, which is hereby incorporated by reference.

FIG. 2B illustrates example components of an IM container applicable toone or more embodiments. It should be understood that an IM containermay include a different set of components than the componentsillustrated in FIG. 2B or described in the various examples herein. AnIM container may include more or fewer component types than aconstruct-based container.

As an example, an IM container corresponds to a class file 200 b. Classfile 200 b generated by the container-based language runtime may notnecessarily exist as a separate referenceable “file” outside of thecontainer-based language runtime. A developer may be unable to referenceclass file 200 b for any purpose. The class file 200 b may be associatedwith metadata 227 referenced by the container-based language runtime.Metadata 227 may include information regarding the location ofattributes of isolated methods. Metadata 227 may include for example, anoffset corresponding to an object array 221 (or portion thereof) that isassociated with a particular isolated method. Method structures 229 andan object array 221 may be referred to as being “contained” within classfile 200 b because metadata 227, corresponding to class file 200 b,identifies a memory location corresponding to the object array 221 andthe method structures 229.

In an embodiment, an object array 221 (also referred to herein as a“constants array”) may include objects of any primitive or non-primitivetype that are passed in as parameters of a code loader method forloading isolated methods. The object array 221 may provide a higherlevel of abstraction than a typical “Constant Pool” described above inrelation to FIG. 2A. In an embodiment, all type variables correspondingto the object array 221 for a particular IM may belong solely to theparticular IM and inaccessible by other IMs. In other embodiments, ashared object array 221 may be implemented for multiple IMs within asame IM container.

2.3 Example Virtual Machine Architecture

FIG. 3 illustrates an example virtual machine memory layout 300 in blockdiagram form according to an embodiment. In order to provide clearexamples, the remaining discussion will assume that the virtual machine104 adheres to the virtual machine memory layout 300 depicted in FIG. 3.In addition, although components of the virtual machine memory layout300 may be referred to as memory “areas”, there is no requirement thatthe memory areas are contiguous.

In the example illustrated by FIG. 3, the virtual machine memory layout300 is divided into a shared area 301 and a thread area 307. The sharedarea 301 represents an area in memory where structures shared among thevarious threads executing on the virtual machine 104 are stored. Theshared area 301 includes a heap 302 and a per-class area 303. In anembodiment, the heap 302 represents the run-time data area from whichmemory for class instances and arrays is allocated. In an embodiment,the per-class area 303 represents the memory area where the datapertaining to the individual classes are stored. In an embodiment, theper-class area 303 includes, for each loaded class, a run-time constantpool 304 representing data from the constant table 201 of the class,field and method data 306 (for example, to hold the static fields of theclass), and the method code 305 representing the virtual machineinstructions for methods of the class.

In an embodiment, Isolated Method Containers area 314 represents thememory area where the data pertaining to isolated methods is stored. TheIM containers area 314 (IM containers) may not necessarily be separatefrom the per-class area 303 (construct-based containers). The per-classarea 303 and IM containers area 314 are illustrated separately forpurposes of explanation. The IM containers area 314 include attributesof IM methods stored in an IM container(s). The method code 315represents the virtual machine instructions for isolated methods passedin as parameters of a code loader method. The object array correspondingto the IM methods may include class instances which may be stored inheap 302. The IM containers area 314 may include a smaller memoryfootprint than the per-class area 303 corresponding to construct-basedcontainers.

The thread area 307 represents a memory area where structures specificto individual threads are stored. In FIG. 3, the thread area 307includes thread structures 308 and thread structures 311, representingthe per-thread structures utilized by different threads. In order toprovide clear examples, the thread area 307 depicted in FIG. 3 assumestwo threads are executing on the virtual machine 104. However, in apractical environment, the virtual machine 104 may execute any arbitrarynumber of threads, with the number of thread structures scaledaccordingly.

In an embodiment, thread structures 308 includes program counter 309 andvirtual machine stack 310. Similarly, thread structures 311 includesprogram counter 312 and virtual machine stack 313. In an embodiment,program counter 309 and program counter 312 store the current address ofthe virtual machine instruction being executed by their respectivethreads.

Thus, as a thread steps through the instructions, the program countersare updated to maintain an index to the current instruction. In anembodiment, virtual machine stack 310 and virtual machine stack 313 eachstore frames for their respective threads that hold local variables andpartial results, and is also used for method invocation and return.

In an embodiment, a frame is a data structure used to store data andpartial results, return values for methods, and perform dynamic linking.A new frame is created each time a method is invoked. A frame isdestroyed when the method that caused the frame to be generatedcompletes. Thus, when a thread performs a method invocation, the virtualmachine 104 generates a new frame and pushes that frame onto the virtualmachine stack associated with the thread.

When the method invocation completes, the virtual machine 104 passesback the result of the method invocation to the previous frame and popsthe current frame off of the stack. In an embodiment, for a giventhread, one frame is active at any point. This active frame is referredto as the current frame, the method that caused generation of thecurrent frame is referred to as the current method, and the class towhich the current method belongs is referred to as the current class.

FIG. 4 illustrates an example frame 400 in block diagram form accordingto an embodiment. In order to provide clear examples, the remainingdiscussion will assume that frames of virtual machine stack 310 andvirtual machine stack 313 adhere to the structure of frame 400.

In an embodiment, frame 400 includes local variables 401, operand stack402, and run-time constant pool reference table 403. In an embodiment,the local variables 401 are represented as an array of variables thateach hold a value, for example, Boolean, byte, char, short, int, float,or reference. Further, some value types, such as longs or doubles, maybe represented by more than one entry in the array. The local variables401 are used to pass parameters on method invocations and store partialresults. For example, when generating the frame 400 in response toinvoking a method, the parameters may be stored in predefined positionswithin the local variables 401, such as indexes 1-N corresponding to thefirst to Nth parameters in the invocation.

In an embodiment, the operand stack 402 is empty by default when theframe 400 is created by the virtual machine 104. The virtual machine 104then supplies instructions from the method code 305 of the currentmethod to load constants or values from the local variables 501 onto theoperand stack 502. Other instructions take operands from the operandstack 402, operate on them, and push the result back onto the operandstack 402. Furthermore, the operand stack 402 is used to prepareparameters to be passed to methods and to receive method results. Forexample, the parameters of the method being invoked could be pushed ontothe operand stack 402 prior to issuing the invocation to the method. Thevirtual machine 104 then generates a new frame for the method invocationwhere the operands on the operand stack 402 of the previous frame arepopped and loaded into the local variables 401 of the new frame. Whenthe invoked method terminates, the new frame is popped from the virtualmachine stack and the return value is pushed onto the operand stack 402of the previous frame.

In an embodiment, the run-time constant pool reference table 403contains a reference to the run-time constant pool 304 of the currentclass. The run-time constant pool reference table 403 is used to supportresolution. Resolution is the process whereby symbolic references in theconstant pool 304 are translated into concrete memory addresses, loadingclasses as necessary to resolve as-yet-undefined symbols and translatingvariable accesses into appropriate offsets into storage structuresassociated with the run-time location of these variables.

2.4 Loading, Linking, and Initializing Classes

In an embodiment, the virtual machine 104 dynamically loads, links, andinitializes classes. Loading is the process of finding a class with aparticular name and creating a representation from the associated classfile 200 a of that class within the memory of the runtime environment113. For example, creating the run-time constant pool 304, method code305, and field and method data 306 for the class within the per-classarea 303 of the virtual machine memory layout 300. Linking is theprocess of taking the in-memory representation of the class andcombining it with the run-time state of the virtual machine 104 so thatthe methods of the class can be executed. Initialization is the processof executing the class constructors to set the starting state of thefield and method data 306 of the class and/or create class instances onthe heap 302 for the initialized class.

The following are examples of loading, linking, and initializingtechniques that may be implemented by the virtual machine 104. However,in many embodiments the steps may be interleaved, such that an initialclass is loaded, then during linking a second class is loaded to resolvea symbolic reference found in the first class, which in turn causes athird class to be loaded, and so forth. Thus, progress through thestages of loading, linking, and initializing can differ from class toclass. Further, some embodiments may delay (perform “lazily”) one ormore functions of the loading, linking, and initializing process untilthe class is actually required. For example, resolution of a methodreference may be delayed until a virtual machine instruction invokingthe method is executed. Thus, the exact timing of when the steps areperformed for each class can vary greatly between implementations.

To begin the loading process, the virtual machine 104 starts up byinvoking the class loader 107 which loads an initial class. Thetechnique by which the initial class is specified will vary fromembodiment to embodiment. For example, one technique may have thevirtual machine 104 accept a command line argument on startup thatspecifies the initial class.

To load a class, the class loader 107 parses the class file 200 acorresponding to the class and determines whether the class file 200 ais well-formed (meets the syntactic expectations of the virtual machine104). If not, the class loader 107 generates an error. For example, inJava the error might be generated in the form of an exception which isthrown to an exception handler for processing. Otherwise, the classloader 107 generates the in-memory representation of the class byallocating the run-time constant pool 304, method code 305, and fieldand method data 306 for the class within the per-class area 303.

In some embodiments, when the class loader 107 loads a class, the classloader 107 also recursively loads the super-classes of the loaded class.For example, the virtual machine 104 may ensure that the superclasses ofa particular class are loaded, linked, and/or initialized beforeproceeding with the loading, linking and initializing process for theparticular class.

During linking, the virtual machine 104 verifies the class, prepares theclass, and performs resolution of the symbolic references defined in therun-time constant pool 304 of the class.

To verify the class, the virtual machine 104 checks whether thein-memory representation of the class is structurally correct. Forexample, the virtual machine 104 may check that each class except thegeneric class Object has a superclass, check that final classes have nosub-classes and final methods are not overridden, check whether constantpool entries are consistent with one another, check whether the currentclass has correct access permissions for classes/fields/structuresreferenced in the constant pool 304, check that the virtual machine 104code of methods will not cause unexpected behavior (e.g. making sure ajump instruction does not send the virtual machine 104 beyond the end ofthe method), and so forth. The exact checks performed duringverification are dependent on the implementation of the virtual machine104. In some cases, verification may cause additional classes to beloaded, but does not necessarily require those classes to also be linkedbefore proceeding. For example, assume Class A contains a reference to astatic field of Class B. During verification, the virtual machine 104may check Class B to ensure that the referenced static field actuallyexists, which might cause loading of Class B, but not necessarily thelinking or initializing of Class B. However, in some embodiments,certain verification checks can be delayed until a later phase, such asbeing checked during resolution of the symbolic references. For example,some embodiments may delay checking the access permissions for symbolicreferences until those references are being resolved.

To prepare a class, the virtual machine 104 initializes static fieldslocated within the field and method data 306 for the class to defaultvalues. In some cases, setting the static fields to default values maynot be the same as running a constructor for the class. For example, theverification process may zero out or set the static fields to valuesthat the constructor would expect those fields to have duringinitialization.

During resolution, the virtual machine 104 dynamically determinesconcrete memory address from the symbolic references included in therun-time constant pool 304 of the class. To resolve the symbolicreferences, the virtual machine 104 utilizes the class loader 107 toload the class identified in the symbolic reference (if not alreadyloaded). Once loaded, the virtual machine 104 has knowledge of thememory location within the per-class area 303 of the referenced classand its fields/methods. The virtual machine 104 then replaces thesymbolic references with a reference to the concrete memory location ofthe referenced class, field, or method. In an embodiment, the virtualmachine 104 caches resolutions to be reused in case the sameclass/name/descriptor is encountered when the virtual machine 104processes another class. For example, in some cases, class A and class Bmay invoke the same method of class C. Thus, when resolution isperformed for class A, that result can be cached and reused duringresolution of the same symbolic reference in class B to reduce overhead.

In some embodiments, the step of resolving the symbolic referencesduring linking is optional. For example, an embodiment may perform thesymbolic resolution in a “lazy” fashion, delaying the step of resolutionuntil a virtual machine instruction that requires the referencedclass/method/field is executed.

During initialization, the virtual machine 104 executes the constructorof the class to set the starting state of that class. For example,initialization may initialize the field and method data 306 for theclass and generate/initialize any class instances on the heap 302created by the constructor. For example, the class file 200 a for aclass may specify that a particular method is a constructor that is usedfor setting up the starting state. Thus, during initialization, thevirtual machine 104 executes the instructions of that constructor.

In some embodiments, the virtual machine 104 performs resolution onfield and method references by initially checking whether thefield/method is defined in the referenced class. Otherwise, the virtualmachine 104 recursively searches through the super-classes of thereferenced class for the referenced field/method until the field/methodis located, or the top-level superclass is reached, in which case anerror is generated.

3. Loading an Isolated Method

One or more embodiments include loading an Isolated Method (IM) by acontainer-based language runtime. As described above, an IM is notincluded as a component of a construct in a container-based languageframework. An IM may be loaded, for example, by executing another methodwhich accepts the attributes of the IM, specified in bytecode, asparameters. FIG. 5 illustrates an example set of operations for loadingan Isolated Method (IM) by a container-based language runtime inaccordance with one or more embodiments.

Operations described below with reference to FIG. 5 may be rearranged,omitted, or modified. Additional operations, not described below, may beperformed instead of or in addition to the described operations.Accordingly, the operations as recited below should not be construed tolimit the scope of any of the claims recited herein.

One or more embodiments include a compiler compiling a construct (e.g.,a class) in a container-based language framework that includes a codeloader method (Operation 502). Compiling a construct includes convertingsource code to bytecode organized as a set of one or moreconstruct-based containers that may be processed by the container-basedlanguage runtime. In the instant application, a code loader method,which may have any name, is referred to herein and named loadCode forease of explanation. The method loadCode may be included in a particularconstruct which is compiled to generate a construct-based container withexecutable instructions, in bytecode, that correspond to the loadCodemethod. In one embodiment, a code loader method such as the loadCodemethod is declared as:

MethodHandle loadCode (String name, MethodType type, byte[ ]instructions, Object[ ] constants)

The parameters of the loadCode method include method attributescorresponding to the IM method. The name parameter of the loadCodemethod determines the IM's name. The type parameter of the loadCodemethod determines the IM's return type and parameter types. Theinstructions array includes the IM's bytecode instructions. The IM'sbytecode instructions may include indices into the constants array ofinstantiated objects which serves as a method-local constant poolsubstitute.

In contrast to IMs, methods defined as components of constructs (e.g.,classes) would be converted to bytecode instructions that would appearstatically in a construct-based container (e.g., a class file generatedby compiling a class). The bytecode instructions, in a construct-basedcontainer, typically include indices into a class' constant pool.

In an embodiment, a code loader method, which loads an IM, returns a“handle” for referencing and/or invoking the IM after the IM is loaded.MethodHandle, recited as a return type in the example loadCodedeclaration above, is a type corresponding tojava.lang.invoke.MethodHandle in the Java API. MethodHandle may be usedas a reference to the IM being loaded. MethodHandle may be used toinvoke the IM after the IM is loaded. When an object of typeMethodHandle is instantiated with a reference to a particular IM, theMethodHandle is referred to as a “live” reference to the IM. In othercontainer-based language runtimes, other types of “handles” may beimplemented for referencing a loaded IM.

In an embodiment, the code loader method is executed by acontainer-based language runtime for loading an IM (Operation 504). Asdescribed above, the attributes of the IM are passed as parameters ofthe code loader method. The attributes of the IM may be read frommemory, input via a user interface, retrieved by execution of anoperation, or otherwise obtained by a thread which invokes the codeloader method. The thread invokes the code loader method, loadCode withthe attributes of the IM to be loaded.

A check may be performed to determine if the thread (or construct-basedcontainer) invoking the loadCode method has the permissions necessaryfor loading the IM (Operation 506). Since the loadCode method allows fordirectly loading bytecode into a runtime environment (without acompilation-time check of the IM), security checks may be crucial inavoiding malicious attacks or major errors. Checking permissions mayalso include determining if the thread has permission for accessing thetypes (e.g., MethodHandle) corresponding to the invocation of theloadCode method. If the thread invoking the loadCode method does nothave sufficient permissions, then the IM is not loaded.

If the thread for invoking the loadCode method has sufficientpermissions, then operations are initiated to load the IM into an IMcontainer. A check may be performed to determine whether an IMcontainer, for loading the IM, has already been generated by thecontainer-based language runtime (Operation 508). In an example, a fieldmay be maintained for each module in a module system which identifies anIM container generated for the module, or an indication that an IMcontainer has not been generated. Based on the status of the field, adetermination is made as to whether the IM container has been generatedfor the IM to be loaded. In another example, a single IM container isused for all IMs. The single IM container may be generated by thecontainer-based language runtime once a method for loading the first IMrequiring an IM container is executed. Alternatively, the IM containermay be generated by default as soon as the container-based languageruntime begins execution. If the IM container is generated by default,then Operation 508 and Operation 510 may be skipped.

In an embodiment, an amount of memory allocated to the IM container isexamined to determine if sufficient memory is available for assignmentto the new IM to be loaded. If insufficient memory is available, then anamount of memory allocated to the IM container may be increased.Additional non-continguous memory may be allocated to the IM container,resulting in an increase in a size of of the IM container.

If an IM container has not been generated when the IM is to be loaded,then the IM container is generated by the container-based languageruntime (Operation 510). Generating an IM container may includegenerating a container that is the same in structure or different instructure than a construct-based container. Different implementationsmay include different IM container memory specifications. Generating theIM container may include allocating memory similar to how memory isallocated for a construct-based container (e.g., class file). An IMcontainer may be expected to grow without a limit, or up to a certaindefined limit for adding new IMs. Memory location and/or memory sizeallocated for an IM container may be based on expected behavior orconfigured limitations of the IM container.

In an embodiment, an IM is loaded as a component of an IM container(Operation 512). Bytecode instructions corresponding to the IM areloaded into the memory allocated for the IM container. The IM containermetadata is updated to identify the location of the bytecodeinstructions corresponding to the IM. The objects (e.g., classinstances) that are received as parameters of the code loader method arestored in an object array within the IM container, or in a separatelymaintained object array. Access to the objects in the object array maybe restricted only to the corresponding IM loaded with the objects or tomultiple IMs within the same IM container. The bytecode instructions maythemselves be modified to reference the location of respectivereferenced objects. Alternatively, a translation table or offset may beapplied to the location referenced in bytecode instructions to determinethe location of the respective referenced objects loaded by thecontainer-based language runtime. In an embodiment, duplicates withinthe set of objects referenced by a set of IMs may be removed to reducethe memory footprint of the objects.

In an embodiment, loading an IM includes returning a method handle (orany other type of live reference that may used to reference or invokethe IM) to the thread that invoked the code loader method for loadingthe IM. The method handle may be stored as a thread-local field managedby the thread. The method handle serves as a “live” reference to the IM.If the thread terminates, the IM may no longer be referenceable orinvoke-able even though other IMs in the same IM container may continueto be referenceable and invoke-able.

Once an IM is loaded as a component of an IM container, the IM may beinvoked (Operation 514). In one or embodiments, the IM is invoked usinga method handle that was returned to the thread executing the codeloader method for loading the IM. Invoking the IM may include thecontainer-based language runtime accessing the IM containercorresponding to the IM. The metadata within the IM container may beused to identify a location of the first bytecode instruction of the IMto be executed.

4. Garbage Collection of Container Components

One or more embodiments include optimizing the garbage collectionprocesses for IM containers maintained by a container-based languageruntime. As noted above, IMs may be referenced and/or invoked usingmethod handles that are generated when an IM is loaded. Furthermore,when an IM is loaded, corresponding memory space may be allocated to a“stretchable” and “shrinkable” IM container that includes the IM.

FIG. 6 illustrates a garbage collection process for reclaiming portionsof memory allocated to an IM container in accordance with one or moreembodiments. The garbage collection process is periodically executed tore-claim memory from the IM container corresponding to IMs that are nolonger referenceable or invoke-able.

In each execution, the garbage collection process, identifies IMs forwhich memory is currently allocated in an IM container (Operation 602).As an example, a disassembler (e.g., a Java class file disassembler) maybe executed periodically to determine the contents of an IM container.The disassembler traverses the contents of the IM container. Thedisassembler identifies each IM within the IM container as a componentof the IM container. IMs identified by the disassembler are determinedto be IMs for which memory is currently allocated in the IM container.

For each identified IM, a determination is made as to whether the IM hasa “live” reference (Operation 604). A “live” reference is an object(e.g., a method handle) that has been instantiated and is stillaccessible by at least one currently executing thread. The method handleor “live” reference may have been instantiated by a thread as athread-local field when the IM was loaded. When the thread isterminated, the method handle is no longer a “live” reference. Inanother example, the method handle may be instantiated by a thread as aglobal variable accessible by many different threads. The method handlecontinues to be a “live” reference to the IM as long as one of thethreads are still executing and able to access the method handle.

If the IM does not have any “live” references remaining, then the IMcannot be invoked. The memory space corresponding to the IM within thecontainer is de-allocated (Operation 606). A garbage collection processmay then re-claim the de-allocated memory (Operation 608). As a resultof de-allocation of a a portion of the memory allocated to IM of the IMcontainer, the IM container shrinks in size. If new IMs are added to theIM container, additional memory may be allocated to the IM container.New IMs being added to the IM container may result in an increase of theIM container size.

In an embodiment, memory allocated for an IM that does not have any“live” references is retained by the IM container. The IM containeroverwrites the memory with information corresponding to one or more newIMs with “live” references.

5. Miscellaneous; Extensions

Embodiments are directed to a system with one or more devices thatinclude a hardware processor and that are configured to perform any ofthe operations described herein and/or recited in any of the claimsbelow.

In an embodiment, a non-transitory computer readable storage mediumcomprises instructions which, when executed by one or more hardwareprocessors, causes performance of any of the operations described hereinand/or recited in any of the claims.

Any combination of the features and functionalities described herein maybe used in accordance with one or more embodiments. In the foregoingspecification, embodiments have been described with reference tonumerous specific details that may vary from implementation toimplementation. The specification and drawings are, accordingly, to beregarded in an illustrative rather than a restrictive sense. The soleand exclusive indicator of the scope of the invention, and what isintended by the applicants to be the scope of the invention, is theliteral and equivalent scope of the set of claims that issue from thisapplication, in the specific form in which such claims issue, includingany subsequent correction.

6. Hardware Overview

According to one embodiment, the techniques described herein areimplemented by one or more special-purpose computing devices. Thespecial-purpose computing devices may be hard-wired to perform thetechniques, or may include digital electronic devices such as one ormore application-specific integrated circuits (ASICs) or fieldprogrammable gate arrays (FPGAs) that are persistently programmed toperform the techniques, or may include one or more general purposehardware processors programmed to perform the techniques pursuant toprogram instructions in firmware, memory, other storage, or acombination. Such special-purpose computing devices may also combinecustom hard-wired logic, ASICs, or FPGAs with custom programming toaccomplish the techniques. The special-purpose computing devices may bedesktop computer systems, portable computer systems, handheld devices,networking devices or any other device that incorporates hard-wiredand/or program logic to implement the techniques.

For example, FIG. 7 is a block diagram that illustrates a computersystem 700 upon which an embodiment of the invention may be implemented.Computer system 700 includes a bus 702 or other communication mechanismfor communicating information, and a hardware processor 704 coupled withbus 702 for processing information. Hardware processor 704 may be, forexample, a general purpose microprocessor.

Computer system 700 also includes a main memory 706, such as a randomaccess memory (RAM) or other dynamic storage device, coupled to bus 702for storing information and instructions to be executed by processor704. Main memory 706 also may be used for storing temporary variables orother intermediate information during execution of instructions to beexecuted by processor 704. Such instructions, when stored innon-transitory storage media accessible to processor 704, rendercomputer system 700 into a special-purpose machine that is customized toperform the operations specified in the instructions.

Computer system 700 further includes a read only memory (ROM) 708 orother static storage device coupled to bus 702 for storing staticinformation and instructions for processor 704. A storage device 710,such as a magnetic disk or optical disk, is provided and coupled to bus702 for storing information and instructions.

Computer system 700 may be coupled via bus 702 to a display 712, such asa cathode ray tube (CRT), for displaying information to a computer user.An input device 714, including alphanumeric and other keys, is coupledto bus 702 for communicating information and command selections toprocessor 704. Another type of user input device is cursor control 716,such as a mouse, a trackball, or cursor direction keys for communicatingdirection information and command selections to processor 704 and forcontrolling cursor movement on display 712. This input device typicallyhas two degrees of freedom in two axes, a first axis (e.g., x) and asecond axis (e.g., y), that allows the device to specify positions in aplane.

Computer system 700 may implement the techniques described herein usingcustomized hard-wired logic, one or more ASICs or FPGAs, firmware and/orprogram logic which in combination with the computer system causes orprograms computer system 700 to be a special-purpose machine. Accordingto one embodiment, the techniques herein are performed by computersystem 700 in response to processor 704 executing one or more sequencesof one or more instructions contained in main memory 706. Suchinstructions may be read into main memory 706 from another storagemedium, such as storage device 710. Execution of the sequences ofinstructions contained in main memory 706 causes processor 704 toperform the process steps described herein. In alternative embodiments,hard-wired circuitry may be used in place of or in combination withsoftware instructions.

The term “storage media” as used herein refers to any non-transitorymedia that store data and/or instructions that cause a machine tooperation in a specific fashion. Such storage media may comprisenon-volatile media and/or volatile media. Non-volatile media includes,for example, optical or magnetic disks, such as storage device 710.Volatile media includes dynamic memory, such as main memory 706. Commonforms of storage media include, for example, a floppy disk, a flexibledisk, hard disk, solid state drive, magnetic tape, or any other magneticdata storage medium, a CD-ROM, any other optical data storage medium,any physical medium with patterns of holes, a RAM, a PROM, and EPROM, aFLASH-EPROM, NVRAM, any other memory chip or cartridge.

Storage media is distinct from but may be used in conjunction withtransmission media. Transmission media participates in transferringinformation between storage media. For example, transmission mediaincludes coaxial cables, copper wire and fiber optics, including thewires that comprise bus 702. Transmission media can also take the formof acoustic or light waves, such as those generated during radio-waveand infra-red data communications.

Various forms of media may be involved in carrying one or more sequencesof one or more instructions to processor 704 for execution. For example,the instructions may initially be carried on a magnetic disk or solidstate drive of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 700 canreceive the data on the telephone line and use an infra-red transmitterto convert the data to an infra-red signal. An infra-red detector canreceive the data carried in the infra-red signal and appropriatecircuitry can place the data on bus 702. Bus 702 carries the data tomain memory 706, from which processor 704 retrieves and executes theinstructions. The instructions received by main memory 706 mayoptionally be stored on storage device 710 either before or afterexecution by processor 704.

Computer system 700 also includes a communication interface 718 coupledto bus 702. Communication interface 718 provides a two-way datacommunication coupling to a network link 720 that is connected to alocal network 722. For example, communication interface 718 may be anintegrated services digital network (ISDN) card, cable modem, satellitemodem, or a modem to provide a data communication connection to acorresponding type of telephone line. As another example, communicationinterface 718 may be a local area network (LAN) card to provide a datacommunication connection to a compatible LAN. Wireless links may also beimplemented. In any such implementation, communication interface 718sends and receives electrical, electromagnetic or optical signals thatcarry digital data streams representing various types of information.

Network link 720 typically provides data communication through one ormore networks to other data devices. For example, network link 720 mayprovide a connection through local network 722 to a host computer 724 orto data equipment operated by an Internet Service Provider (ISP) 726.ISP 726 in turn provides data communication services through the worldwide packet data communication network now commonly referred to as the“Internet” 728. Local network 722 and Internet 728 both use electrical,electromagnetic or optical signals that carry digital data streams. Thesignals through the various networks and the signals on network link 720and through communication interface 718, which carry the digital data toand from computer system 700, are example forms of transmission media.

Computer system 700 can send messages and receive data, includingprogram code, through the network(s), network link 720 and communicationinterface 718. In the Internet example, a server 730 might transmit arequested code for an application program through Internet 728, ISP 726,local network 722 and communication interface 718.

The received code may be executed by processor 704 as it is received,and/or stored in storage device 710, or other non-volatile storage forlater execution.

In the foregoing specification, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense. The sole and exclusive indicator of the scope of the invention,and what is intended by the applicants to be the scope of the invention,is the literal and equivalent scope of the set of claims that issue fromthis application, in the specific form in which such claims issue,including any subsequent correction.

What is claimed is:
 1. One or more non-transitory machine-readable mediastoring instructions which, when executed by one or more processors,cause: identifying, by a container-based language runtime, a firstinstruction in a first module to load a first set of instructions as afirst method; responsive to the first instruction in the first module:determining, by the container-based language runtime, that a firstcontainer is associated with methods loaded using the first instructionfrom the first module; selecting, by the container-based languageruntime, the first container for being associated with the first method;loading, by the container-based language runtime, the first set ofinstructions corresponding to the first method as a component of thefirst container; identifying, by the container-based language runtime, asecond instruction to execute the first method; responsive to the secondinstruction: executing, by the contain-based language runtime, the firstset of instructions corresponding to the first method and stored inassociation with the first container; identifying, by thecontainer-based language runtime, the first instruction in a secondmodule to load a second set of instructions as a second method;responsive to the first instruction in the second module: determining,by the container-based language runtime, that a second container isassociated with methods loaded using the first instruction from thesecond module; selecting, by the container-based language runtime, thesecond container for being associated with the second method; loading,by the container-based language runtime, the second set of instructionscorresponding to the second method as a component of the secondcontainer; identifying, by the container-based language runtime, a thirdinstruction to execute the second method; responsive to the thirdinstruction: executing, by the contain-based language runtime, thesecond set of instructions corresponding to the second method and storedin association with the second container.
 2. The one or more media ofclaim 1, further storing instructions which cause: identifying, by thecontainer-based language runtime, the first instruction in the firstmodule to load a third set of instructions as a third method; responsiveto the first instruction in the first module: determining, by thecontainer-based language runtime, that the first container is associatedwith methods loaded using the first instruction from the first module;selecting, by the container-based language runtime, the first containerfor being associated with the third method; loading, by thecontainer-based language runtime, the third set of instructionscorresponding to the third method as a component of the first container;identifying, by the container-based language runtime, a fourthinstruction to execute the third method; responsive to the fourthinstruction: executing, by the contain-based language runtime, the thirdset of instructions corresponding to the third method and stored inassociation with the first container.
 3. The one or more media of claim1, wherein determining, by the container-based language runtime, thatthe first container is associated with methods loaded using the firstinstruction from the first module comprises: determining that a fieldmaintained for the first module identifies the first container as beingassociated with the first module.
 4. The one or more media of claim 1,wherein determining, by the container-based language runtime, that thefirst container is associated with methods loaded using the firstinstruction from the first module comprises: determining that a fieldmaintained for the first module indicates that a container associatedwith the first module has been generated.
 5. The one or more media ofclaim 1, wherein determining, by the container-based language runtime,that the first container is associated with methods loaded using thefirst instruction from the first module comprises: generating, by thecontainer-based language runtime, the first container for the firstmodule.
 6. The one or more media of claim 1, wherein the first containerwas previously generated during the loading of another method using thefirst instruction from the first module.
 7. The one or more media ofclaim 1, wherein the first container is a stretchable container suchthat an amount of memory allocated to the container may be increased. 8.The one or more media of claim 1, wherein the first container is ashrinkable container such that an amount of memory allocated to thecontainer may be decreased.
 9. The one or more media of claim 1, whereinthe first method is an isolated method.
 10. The one or more media ofclaim 1, wherein the first container is a first-order container.
 11. Theone or more media of claim 1, wherein the first container is ahighest-hierarchical level data structure referenced by thecontainer-based language runtime.
 12. The one or more media of claim 1,wherein the first set of instructions are bytecode instructions.
 13. Theone or more media of claim 1, wherein the first set of instructions areexecutable by the container-based runtime without requiring conversionto a different language or format.
 14. The one or more media of claim 1,wherein the first set of instructions are interpretable by thecontainer-based language runtime.
 15. The one or more media of claim 1,wherein an identifier corresponding to the container is directlyreferenced by the container-based language runtime while executing oneor more operations.
 16. The one or more media of claim 1, wherein priorto loading the first set of instructions corresponding to the firstmethod as the component of the first container: increasing, by thecontainer-based language runtime, an amount of memory allocated to thefirst container.
 17. A system, comprising: one or more devices, eachincluding at least one hardware processor; and the system beingconfigured to perform operations comprising: identifying, by acontainer-based language runtime, a first instruction in a first moduleto load a first set of instructions as a first method; responsive to thefirst instruction in the first module: determining, by thecontainer-based language runtime, that a first container is associatedwith methods loaded using the first instruction from the first module;selecting, by the container-based language runtime, the first containerfor being associated with the first method; loading, by thecontainer-based language runtime, the first set of instructionscorresponding to the first method as a component of the first container;identifying, by the container-based language runtime, a secondinstruction to execute the first method; responsive to the secondinstruction: executing, by the contain-based language runtime, the firstset of instructions corresponding to the first method and stored inassociation with the first container; identifying, by thecontainer-based language runtime, the first instruction in a secondmodule to load a second set of instructions as a second method;responsive to the first instruction in the second module: determining,by the container-based language runtime, that a second container isassociated with methods loaded using the first instruction from thesecond module; selecting, by the container-based language runtime, thesecond container for being associated with the second method; loading,by the container-based language runtime, the second set of instructionscorresponding to the second method as a component of the secondcontainer; identifying, by the container-based language runtime, a thirdinstruction to execute the second method; responsive to the thirdinstruction: executing, by the contain-based language runtime, thesecond set of instructions corresponding to the second method and storedin association with the second container.
 18. The system of claim 17,wherein the operations further comprise: identifying, by thecontainer-based language runtime, the first instruction in the firstmodule to load a third set of instructions as a third method; responsiveto the first instruction in the first module: determining, by thecontainer-based language runtime, that the first container is associatedwith methods loaded using the first instruction from the first module;selecting, by the container-based language runtime, the first containerfor being associated with the third method; loading, by thecontainer-based language runtime, the third set of instructionscorresponding to the third method as a component of the first container;identifying, by the container-based language runtime, a fourthinstruction to execute the third method; responsive to the fourthinstruction: executing, by the contain-based language runtime, the thirdset of instructions corresponding to the third method and stored inassociation with the first container.
 19. A method, comprising:identifying, by a container-based language runtime, a first instructionin a first module to load a first set of instructions as a first method;responsive to the first instruction in the first module: determining, bythe container-based language runtime, that a first container isassociated with methods loaded using the first instruction from thefirst module; selecting, by the container-based language runtime, thefirst container for being associated with the first method; loading, bythe container-based language runtime, the first set of instructionscorresponding to the first method as a component of the first container;identifying, by the container-based language runtime, a secondinstruction to execute the first method; responsive to the secondinstruction: executing, by the contain-based language runtime, the firstset of instructions corresponding to the first method and stored inassociation with the first container; identifying, by thecontainer-based language runtime, the first instruction in a secondmodule to load a second set of instructions as a second method;responsive to the first instruction in the second module: determining,by the container-based language runtime, that a second container isassociated with methods loaded using the first instruction from thesecond module; selecting, by the container-based language runtime, thesecond container for being associated with the second method; loading,by the container-based language runtime, the second set of instructionscorresponding to the second method as a component of the secondcontainer; identifying, by the container-based language runtime, a thirdinstruction to execute the second method; responsive to the thirdinstruction: executing, by the contain-based language runtime, thesecond set of instructions corresponding to the second method and storedin association with the second container; wherein the method isperformed by one or more devices, each including at least one hardwareprocessor.
 20. The method of claim 19, further comprising: identifying,by the container-based language runtime, the first instruction in thefirst module to load a third set of instructions as a third method;responsive to the first instruction in the first module: determining, bythe container-based language runtime, that the first container isassociated with methods loaded using the first instruction from thefirst module; selecting, by the container-based language runtime, thefirst container for being associated with the third method; loading, bythe container-based language runtime, the third set of instructionscorresponding to the third method as a component of the first container;identifying, by the container-based language runtime, a fourthinstruction to execute the third method; responsive to the fourthinstruction: executing, by the contain-based language runtime, the thirdset of instructions corresponding to the third method and stored inassociation with the first container.